module example3(clk_50MHz,rst_n,Led,Key);

input     clk_50MHz;
input     rst_n;
input  [2:0]  Key;
reg  [3:0]  KeyLast;

output [7:0]  Led;
reg  [7:0]  Led;

reg  [23:0] count1;
reg  [23:0] count2;

reg     Led_on ;
reg     Led_dir ;

//--------------------------------------------------
always@(posedge clk_50MHz or posedge rst_n)
begin
 if(rst_n)
  count1 <= 'd0;
 else
  count1 <= count1 + 'd1;
end

always@(posedge clk_50MHz or posedge rst_n)
begin
 if(rst_n)
  Led <= 'b00000000;
 else if(count1 == 'hFFFFFF && Led_on)
  if(Led == 'b00000000)
   Led <= 'b00000001;
  else
   if(Led_dir == 'b1)
    Led <= {Led[6:0],Led[7]};
   else
    Led <= {Led[0],Led[7:1]};
end

//--------------------------------------------------
always@(count2 or rst_n)
begin
 if(rst_n)
  begin
   Led_on  <= 'b1;
   Led_dir <= 'b0;
   KeyLast <= Key;
  end 
 else if(count2 == 'd5000000)
  begin
   KeyLast <= Key;
    if(KeyLast != 'b000)
     begin
      if(KeyLast[0] == 'b1)  
       Led_on <= ~Led_on;
      else if(KeyLast[1] == 'b1)  
       Led_dir <= 'b1;
      else if(KeyLast[2] == 'b1)
       Led_dir <= 'b0;
     end
  end
end

always@(posedge clk_50MHz or posedge rst_n)
begin
 if(rst_n)
  count2 <= 'd0;
 else
  if(KeyLast != Key && count2 <= 'd5000000)
   count2 <= count2 + 'd1;
  else
   count2 <= 'd0;
end

endmodule

将跑马灯和按键去抖相结合。这次是按键按下去就改变状态，所以判断了一下KeyLast的值。

存在2个问题

1 按下KEY1 如果时间很短的话，可能跑马灯的方向发生了2次改变，即反向只跑了一个灯，就又按原来的顺序跑了

2 按下KEY0，从运行到停止立刻相应，从停止到启动需要一个时间才能启动。

估计这2个问题也可能都涉及到按键去抖部分，也就是这部分可能有问题。需要先分析去抖。